I. Ogurtsov, A. Tihonovschi / Chem.J.Mold. 2008, 3 (1), 112-117The magnetic moment values for T=293K (room temperature) are J’= 3.95BM; J”= 4.04BM. This is in a goodaccordance with experimental data for the complex in acetone eff, 293= 3.99BM (2.82BM per vanadium atom) [13].However calculated plot differ from straight horizontal at eff= 4.48BM (3.17BM per vanadium atom) obtained in [10].The difference may be because <strong>of</strong> the solid state effect (measurements in [10] were carried out for the powder form)and/or temperature independent paramagnetism. The value <strong>of</strong> 4.48BM obtained in [10] is lower than 4.7BM neededfor the ground state with S=2 to be the only populated state. This means that the excited state(s) are populated at roomtemperature too.ConclusionsIt follows from our calculations that the exchange interaction in the [V 2O(bipy) 4Cl 2] 2+ can be envisaged as thesuperexchange <strong>of</strong> the V atoms electronic pairs localized on the magnetic orbitals <strong>of</strong> d- type metal orbitals and <strong>of</strong> thed- type metal orbitals hybridized with p- orbitals <strong>of</strong> the bridge oxygen and bipyridine molecules laying perpendicularlyto V-V axis. In our calculations we have obtained results which are in accordance with experiment - in studied complexthere is a ferromagnetic interaction between centers. The magnetic moment value is predicted with a good adequacy.The ab initio study have confirmed the keeping <strong>of</strong> the Lande rule in energy spectrum <strong>of</strong> the [V 2O(bipy) 4Cl 2] 2+ too.References[1] Armstrong W.H., Spool A., Papaefthymion G.C., Frenkel R.B., Lippard S.J. J. Am. Chem. Soc. 1984, Vol. 106,p. 3653.[2] Gatteschi, D. Adv. Mat. 1994, Vol. 6, p. 635.[3] Dawson J., Gray H.B., Hoenig H.E., Rossmann G.R., Schredder J.M., Wang R-H. Bio<strong>chemistry</strong>. 1972, Vol. 1,3, p. 461.[4] Crawford V.H., Richardson H.W., Wassen J.R., Hodgson D.J., Hatfield W.E. Inorg. Chem. 1976, Vol. 9, p.2107.[5] Glerup J., Hodgson D.J., Pedersen E. Acta Chem. Scand. 1983, Vol. A37, p. 161.[6] Weihe H., Güdel H.U. J. Am. Chem. Soc. 1997, Vol. 119, p. 6539.[7] Kahn, O. Molecular magnetism. N.Y. : VCH Publishers Inc., 1993.[8] Tsukerblat, B. S. Group Theory in Chemistry and Spectroscopy. A Simple Guide to advanced Usage. London :Academic Press, 1994.[9] Weihe H., Güdel H.U. J. Am. Chem. Soc. 1998, Vol. 120, p. 2870.[10] Brand S.G., Edelstein N., Hawkins C.J., Shalim<strong>of</strong>f G., Snow M.R., Tiekink E.R.T. Inorg. Chem. 1990, Vol. 29,pp. 434-438.[11] Granovsky, A. PC GAMESS version 7.0. [Online] http://classic.chem.msu.su/gran/gamess/index.html.[12] Abragam A., Bleaney B. Electron paramagnetic resonance <strong>of</strong> transition ions. Moscow : Mir, 1972. Vol. I.[13] Toma H.E., Santos P.S., Lellis F.T.P. J. Coord. Chem. 1988, Vol. 18, pp. 307-316.117
Chemistry Journal <strong>of</strong> Moldova. M. Gonta General, et al./Chem.J.Mold. Industrial and 2008, Ecological 3 (1), 118-126 Chemistry. 2008, 3 (1), 118-126ESTABLISHMENT OF THE ANTIOXIDANT/ANTIRADICAL ACTIVITYOF THE INHIBITORS USING THE DPPH – RADICALMaria Gonta a *, Gheorghe Duca b , Diana Porubin aaState University <strong>of</strong> Moldova, 60 Mateevici str., Chisinau, Republic <strong>of</strong> MoldovabThe Academy <strong>of</strong> Sciences <strong>of</strong> Moldova, 1 Stefan cel Mare blvd., Chisinau, Republic <strong>of</strong> Moldova* Corresponding author: Phone: (373 22) 57-75-53, Email: mvgonta@yahoo.comAbstract. This research paper presents the results <strong>of</strong> the investigation <strong>of</strong> antioxidant activities <strong>of</strong> various inhibitors,which are constituents <strong>of</strong> winery products: quercitin, rezveratrol, dihydroxyfumaric acid. Also, the antioxidantactivity <strong>of</strong> tartaric and dihydroxyfumaric (DFH 4) acids derivatives has been determined: sodium dihydroxyfumarate,dimethylic ester <strong>of</strong> DFH 4and dimethylic ester <strong>of</strong> tartaric acid. The enotannin extracts obtained from grape seedshave been evaluated: the non-oxidized enotannin extract Eneox and the oxidized one -Enoxil. For the determination<strong>of</strong> the antioxidant/antiradical activity the 2,2-diphenil-1-picrylhidrazil (DPPH) radical was used, which has theabsorption maxima at 517 nm. The efficient concentration EC 50, the stoichiometric value <strong>of</strong> the antioxidant andthe free radical, the antiradical power (1/EC 50) and the number <strong>of</strong> moles <strong>of</strong> DPPH-radical reduced by one mole <strong>of</strong>inhibitor have been calculated for all investigated inhibitors. It was found that catechin, quercitin and DFH 4exhibitthe highest inhibition rate.Keywords: antioxidant activity, DPPH radical, inhibition rate, natural inhibitors from secondary winery materialsOverviewNumerous practical and epidemiological studies have confirmed that the micronutrients, thus the antioxidantsexisting in aliments, are able to inhibit the cancerigenesis through their influence on the molecular level, during theinitiation, promotion and progression stages.In recent times, the most studied compounds were the polyphenols, which are constituents <strong>of</strong> the plants.The antioxidant activity <strong>of</strong> the polyphenols is controlled by the presence <strong>of</strong> the hydroxylic groups in the B ringin 3’ and 4’ positions and in a lesser degree, by the presence <strong>of</strong> the hydroxylic group from the C ring in 4’ position.The flavonols, especially catechin, quercitin, kaempherol and their glucosides are elements <strong>of</strong> the black andgreen teas [5] and red wine [5]. The diets rich in vegetables and fruits, especially in grapes, protect against heartdiseases, various forms <strong>of</strong> cancer [7, 8], methemoglobinemy, and display anti-inflammatory, as well as antimutageniceffects [9]. These protective upshots were attributed, in a great measure, to the antioxidants that include flavonoids aswell as carotenoids and vitamins C and B.The majority <strong>of</strong> the polyphenolic constituents from products (flavonols – like quercitine and kaempherol, flavones– like luteolin, flavonones – like catechin, anthocyanidin, for example, cyanidin and malvidin and their glycosides)presents high efficiency, in comparison to the nutrient antioxidants: vitamins C, E, -carotene, that are easily adsorbedin the intestines [10].The grapes and the wine contain high concentrations <strong>of</strong> antioxidants. Based on the study <strong>of</strong> the overall antioxidantactivity <strong>of</strong> the red wine, we concluded that 54,76% is determined by the contribution <strong>of</strong> catechin and epicatechin, thatform approximately 63,54% <strong>of</strong> the phenolic constituents (191 and 82 mg/l, correspondingly) [10].Fig.1. Chemical structure <strong>of</strong> the catechins present in tea and wine [5]. Catechin-(R 1- OH, R 2- H), gallocatechin-(R 1- OH, R 2- OH), catechingallate (R 1- GA, R 2- H), gallocatechingallate (R 1- GA, R 2- OH)118
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